1. Field
The present embodiments relate to an image processing equipment and a digital camera to apply a noise filtering using a multi-resolution analysis for an obtained image.
2. Description of the Related Art
A noise filtering using a multi-resolution analysis (hereinafter, called as a multi-resolution noise filtering) is known as one of methods to filter low-frequency noises appeared in an image data obtained by a digital camera and so on.
In the multi-resolution noise filtering, a noise filtering is performed for reduced images generated with plurality of reduction ratios, and effects thereof are reflected on the original image in which has an original size. Accordingly, for example, the filtering of the low-frequency noises spreading for several dozen pixels in a row direction and/or a column direction is achieved (refer to Japanese Unexamined Patent Application Publication No. 2000-224421).
For example, a down-sampling process is applied to the original image with reduction ratios of one-fourth respectively in the row direction and the column direction to generate a reduced image in one-sixteenth, and the noise components are extracted from this reduced image. Low-frequency noise components in an original image size are estimated by performing an up-sampling using a linear interpolation, for example, on the extracted noise components. The low-frequency noise components estimated as stated above are subtracted from the original image, and thereby, the low-frequency noise components are filtered from the original image.
In a recent high pixel digital camera, there is a case when the low-frequency noises spreading for several dozen pixels wide appear. It is necessary to prepare a line memory storing an image data in a range larger than a range assumed to be a spread of the low-frequency noises so that the filtering of the low-frequency noises as stated above is performed promptly by a pipeline processing.
However, if such a vast line memory is prepared, a significant increase in a circuit scale is caused, and it leads an increase in cost of an image processing equipment.